The incorporation of zinc salts into oral dental care products to provide beneficial effects such as antiplaque, anticalculus (that is, antitartar), and deodorant properties is well known in the prior art, as disclosed in U.S. Pat. Nos. 4,138,477, 4,416,867, 4,425,325 and 4,568,540. However, the extreme astringency of water soluble zinc salts such as zinc chloride is a major drawback in its use in oral dental care products. In addition to the unpleasant astringent taste in the mouth, the efficacy against plaque, calculus and odor inhibition is short-lived. Usually the complex formation of zinc with anionic liquids such as citrate reduces its astringency but also reduces its solubility.
Accordingly, sparingly soluble zinc salts such as zinc citrate, zinc C.sub.14 -alkyl maleate, zinc benzoate, zinc caproate, zinc carbonate, etc. have been used in dentifrice formulations to prolong the anti-calculus and antiplaque effectiveness of the zinc ions due to the slow dissolution of the zinc salts in the saliva. The sparingly soluble characteristic of these zinc salts promotes longevity of action against plaque and calculus at the expense of initial or immediate efficacy.
U.S. Pat. Nos. 4,425,325 and 4,416,867 have solved the astringency problem associated with zinc compounds in oral compositions, by adding glycine and adjusting the pH within the range of 4.5 and 9.4 in order to maintain the zinc in solution which is less astringent than a pH below 4.5.
U.S. Pat. No. 4,138,477 also discloses a non-astringet oral composition containing a zinc-polymer complex having a pH of 4.5 to 6, formed by the chelation or reaction of a zinc compound with an anionic polymer containing carboxylic, sulfonic and/or phosphonic acid radicals.
U.S. Pat. No. 4,568,540 discloses oral compositions effective in controlling mouth odor, calculus, plaque and caries, containing active zinc ions and fluoride ions, said zinc ions being provided by zinc salts selected from the group consisting of zinc chloride, zinc sulfate and zinc thiocyanate, and a specific buffering agent to maintain a pH of 3.5 to 6.0 in order to permit the fluoride ions and zinc ions to remain in solution and not precipitate out.
U.S. Pat. No. 4,100,269 discloses an anticalculus dentifrice containing a substantially insoluble zinc compound having a solubility not exceeding about 0.5 to 1% by weight (based on the amount of dissolved zinc ion) at 20.degree. C., in order to avoid astringency. The abrasive with said anticalculus dentifrice compositions must not interact with the zinc compound. Therefore, the commonly used phosphate abrasives or polishing agents cannot be used.
In U.S. Pat. No. 4,627,977 an anticalculus oral composition is disclosed containing a water soluble alkali metal polyphosphate salt, a fluoride ion source, and a water soluble alkali metal or ammonium anionic linear polymeric polycarboxylate salt having a molecular weight of 1,000 to 1,000,000.
None of the above cited prior art discloses low astringent oral care products including mouthwash, dentifrice, lozenge, etc., containing a complex of zinc and a polyphosphate which is unusually effective in reducing the astringency of the zinc and simultaneously provide anti-plaque, anti-tartar and anti-odor efficacy.